Millions of Muslims across the world celebrated the start of the Eid al-Fitr holiday Monday that marked the end of the fasting month of Ramadan, but violence broke out in the Philippines and observances were somber in the Gaza war zone.

About 50 Islamic militant Abu Sayyf gunmen opened fire on vehicles traveling to a village feast in the southern Philippines, killing 21 people and wounding 11 more.

Muslims Celebrate Eid al-Fitr

​In Gaza, several hundred people gathered for early-morning prayers at a mosque. But rather than heading to festivities afterwards, some went home while others paid respects to the more than 1,000 Palestinians killed during the three-week conflict between Israel and Hamas militants.

Hundreds of worshippers at the National Mosque in Kuala Lumpur prayed for the victims of two Malaysia Airlines flights - one that was shot down over eastern Ukraine earlier this month and another that disappeared during a flight to Beijing in March.

Eid al-Fitr celebrates the purification achieved during Ramadan - a month of sunrise-to-sunset fasting, one of the five pillars of Islam.